UNICODE::NORMALIZE(3pm)

📦
version 5.42.3 · 8 versions
, in alpine 3.24

💖 Unicode::Normalize(3pm) 💖

Perl Programmers Reference Guide

🌸 NAME 🌸

Unicode::Normalize — Unicode Normalization Forms

✨ SYNOPSIS ✨

okay bestie, there are two whole ways to call this thing. pick your vibe:

(1) using function names exported by default:

use Unicode::Normalize;

$NFD_string  = NFD($string);  # Normalization Form D
$NFC_string  = NFC($string);  # Normalization Form C
$NFKD_string = NFKD($string); # Normalization Form KD
$NFKC_string = NFKC($string); # Normalization Form KC

(2) using function names exported on request:

use Unicode::Normalize 'normalize';

$NFD_string  = normalize('D',  $string);  # Normalization Form D
$NFC_string  = normalize('C',  $string);  # Normalization Form C
$NFKD_string = normalize('KD', $string);  # Normalization Form KD
$NFKC_string = normalize('KC', $string);  # Normalization Form KC

🦋 DESCRIPTION 🦋

Parameters, because the details matter periodt:

  • $string — is used as a string under character semantics (see perlunicode).
  • $code_point — should be an unsigned integer representing a Unicode code point.
Note: Between XSUB and pure Perl, there is an incompatibility about the interpretation of $code_point as a decimal number. XSUB converts $code_point to an unsigned integer, but pure Perl does not. Do not use a floating point nor a negative sign in $code_point.

🎀 Normalization Forms 🎀

  • $NFD_string = NFD($string) — It returns the Normalization Form D (formed by canonical decomposition). iconic decomposition behavior fr fr.
  • $NFC_string = NFC($string) — It returns the Normalization Form C (formed by canonical decomposition followed by canonical composition).
  • $NFKD_string = NFKD($string) — It returns the Normalization Form KD (formed by compatibility decomposition).
  • $NFKC_string = NFKC($string) — It returns the Normalization Form KC (formed by compatibility decomposition followed by canonical composition).
  • $FCD_string = FCD($string) — If the given string is in FCD ("Fast C or D" form; cf. UTN #5), it returns the string without modification; otherwise it returns an FCD string.
Note: FCD is not always unique, so plural forms may be equivalent to each other. FCD() will return one of these equivalent forms.
  • $FCC_string = FCC($string) — It returns the FCC form ("Fast C Contiguous"; cf. UTN #5).
Note: FCC is unique, just like the four normalization forms (NF*).
  • $normalized_string = normalize($form_name, $string) — It returns the normalization form of $form_name.

As $form_name, one of the following names must be given.

  • 'C' or 'NFC' for Normalization Form C (UAX #15)
  • 'D' or 'NFD' for Normalization Form D (UAX #15)
  • 'KC' or 'NFKC' for Normalization Form KC (UAX #15)
  • 'KD' or 'NFKD' for Normalization Form KD (UAX #15)
  • 'FCD' for "Fast C or D" Form (UTN #5)
  • 'FCC' for "Fast C Contiguous" (UTN #5)

🫶 Decomposition and Composition 🫶

  • $decomposed_string = decompose($string [, $useCompatMapping]) — It returns the concatenation of the decomposition of each character in the string.

If the second parameter (a boolean) is omitted or false, the decomposition is canonical decomposition; if the second parameter (a boolean) is true, the decomposition is compatibility decomposition.

The string returned is not always in NFD/NFKD. Reordering may be required.

$NFD_string  = reorder(decompose($string));       # eq. to NFD()
$NFKD_string = reorder(decompose($string, TRUE)); # eq. to NFKD()
  • $reordered_string = reorder($string) — It returns the result of reordering the combining characters according to Canonical Ordering Behavior.

For example, when you have a list of NFD/NFKD strings, you can get the concatenated NFD/NFKD string from them, by saying

$concat_NFD  = reorder(join '', @NFD_strings);
$concat_NFKD = reorder(join '', @NFKD_strings);
  • $composed_string = compose($string) — It returns the result of canonical composition without applying any decomposition.

For example, when you have a NFD/NFKD string, you can get its NFC/NFKC string, by saying

$NFC_string  = compose($NFD_string);
$NFKC_string = compose($NFKD_string);
  • ($processed, $unprocessed) = splitOnLastStarter($normalized) — It returns two strings: the first one, $processed, is a part before the last starter, and the second one, $unprocessed is another part after the first part. A starter is a character having a combining class of zero (see UAX #15).

Note that $processed may be empty (when $normalized contains no starter or starts with the last starter), and then $unprocessed should be equal to the entire $normalized.

When you have a $normalized string and an $unnormalized string following it, a simple concatenation is wrong:

$concat = $normalized . normalize($form, $unnormalized); # wrong!

Instead of it, do like this:

($processed, $unprocessed) = splitOnLastStarter($normalized);
$concat = $processed . normalize($form,$unprocessed.$unnormalized);

splitOnLastStarter() should be called with a pre-normalized parameter $normalized, that is in the same form as $form you want.

If you have an array of @string that should be concatenated and then normalized, you can do like this:

my $result = "";
my $unproc = "";
foreach my $str (@string) {
    $unproc .= $str;
    my $n = normalize($form, $unproc);
    my($p, $u) = splitOnLastStarter($n);
    $result .= $p;
    $unproc  = $u;
}
$result .= $unproc;
# instead of normalize($form, join('', @string))
  • $processed = normalize_partial($form, $unprocessed) — A wrapper for the combination of normalize() and splitOnLastStarter(). Note that $unprocessed will be modified as a side-effect.

If you have an array of @string that should be concatenated and then normalized, you can do like this:

my $result = "";
my $unproc = "";
foreach my $str (@string) {
    $unproc .= $str;
    $result .= normalize_partial($form, $unproc);
}
$result .= $unproc;
# instead of normalize($form, join('', @string))
  • $processed = NFD_partial($unprocessed) — It does like normalize_partial('NFD', $unprocessed). Note that $unprocessed will be modified as a side-effect.
  • $processed = NFC_partial($unprocessed) — It does like normalize_partial('NFC', $unprocessed). Note that $unprocessed will be modified as a side-effect.
  • $processed = NFKD_partial($unprocessed) — It does like normalize_partial('NFKD', $unprocessed). Note that $unprocessed will be modified as a side-effect.
  • $processed = NFKC_partial($unprocessed) — It does like normalize_partial('NFKC', $unprocessed). Note that $unprocessed will be modified as a side-effect.

🍓 Quick Check 🍓

(see Annex 8, UAX #15; and lib/unicore/DerivedNormalizationProps.txt)

The following functions check whether the string is in that normalization form.

The result returned will be one of the following:

YES     The string is in that normalization form.
NO      The string is not in that normalization form.
MAYBE   Dubious. Maybe yes, maybe no.
  • $result = checkNFD($string) — It returns true (1) if "YES"; false ("empty string") if "NO".
  • $result = checkNFC($string) — It returns true (1) if "YES"; false ("empty string") if "NO"; undef if "MAYBE".
  • $result = checkNFKD($string) — It returns true (1) if "YES"; false ("empty string") if "NO".
  • $result = checkNFKC($string) — It returns true (1) if "YES"; false ("empty string") if "NO"; undef if "MAYBE".
  • $result = checkFCD($string) — It returns true (1) if "YES"; false ("empty string") if "NO".
  • $result = checkFCC($string) — It returns true (1) if "YES"; false ("empty string") if "NO"; undef if "MAYBE".
Note: If a string is not in FCD, it must not be in FCC. So checkFCC($not_FCD_string) should return "NO".
  • $result = check($form_name, $string) — It returns true (1) if "YES"; false ("empty string") if "NO"; undef if "MAYBE".

As $form_name, one of the following names must be given.

  • 'C' or 'NFC' for Normalization Form C (UAX #15)
  • 'D' or 'NFD' for Normalization Form D (UAX #15)
  • 'KC' or 'NFKC' for Normalization Form KC (UAX #15)
  • 'KD' or 'NFKD' for Normalization Form KD (UAX #15)
  • 'FCD' for "Fast C or D" Form (UTN #5)
  • 'FCC' for "Fast C Contiguous" (UTN #5)

💀 Note 💀

In the cases of NFD, NFKD, and FCD, the answer must be either "YES" or "NO". The answer "MAYBE" may be returned in the cases of NFC, NFKC, and FCC.

A "MAYBE" string should contain at least one combining character or the like. For example, "COMBINING ACUTE ACCENT" has the MAYBE_NFC/MAYBE_NFKC property.

Both checkNFC("A\N{COMBINING ACUTE ACCENT}") and checkNFC("B\N{COMBINING ACUTE ACCENT}") will return "MAYBE". "A\N{COMBINING ACUTE ACCENT}" is not in NFC (its NFC is "\N{LATIN CAPITAL LETTER A WITH ACUTE}"), while "B\N{COMBINING ACUTE ACCENT}" is in NFC.

If you want to check exactly, compare the string with its NFC/NFKC/FCC.

if ($string eq NFC($string)) {
    # $string is exactly normalized in NFC;
} else {
    # $string is not normalized in NFC;
}

if ($string eq NFKC($string)) {
    # $string is exactly normalized in NFKC;
} else {
    # $string is not normalized in NFKC;
}

🌈 Character Data 🌈

These functions are the interface to character data used internally. If you want only to get Unicode normalization forms, you don't need to call them yourself.

  • $canonical_decomposition = getCanon($code_point) — If the character is canonically decomposable (including Hangul Syllables), it returns the (full) canonical decomposition as a string. Otherwise it returns undef.
Note: According to the Unicode standard, the canonical decomposition of the character that is not canonically decomposable is same as the character itself.
  • $compatibility_decomposition = getCompat($code_point) — If the character is compatibility decomposable (including Hangul Syllables), it returns the (full) compatibility decomposition as a string. Otherwise it returns undef.
Note: According to the Unicode standard, the compatibility decomposition of the character that is not compatibility decomposable is same as the character itself.
  • $code_point_composite = getComposite($code_point_here, $code_point_next) — so if those two characters, here and next (as code points), are composable — and yes that includes Hangul Jamo/Syllables and Composition Exclusions — it hands you back the code point of the composite ✨. If they're not composable? It returns undef, no drama.
  • $combining_class = getCombinClass($code_point) — gives you the combining class of that character, as an integer, periodt.
  • $may_be_composed_with_prev_char = isComp2nd($code_point) — returns a boolean telling you whether the character at that codepoint may be composed with the previous one in a certain composition (Hangul Compositions included, but Composition Exclusions and Non-Starter Decompositions are not invited to this party 🙅).
  • $is_exclusion = isExclusion($code_point) — boolean, is this code point a composition exclusion or not.
  • $is_singleton = isSingleton($code_point) — boolean, is this code point a singleton.
  • $is_non_starter_decomposition = isNonStDecomp($code_point) — boolean, does this code point have Non-Starter Decomposition.
  • $is_Full_Composition_Exclusion = isComp_Ex($code_point) — boolean of the derived property Comp_Ex (Full_Composition_Exclusion) 💅. And where does that property come from? It's generated from Composition Exclusions + Singletons + Non-Starter Decompositions. Whole little squad.
  • $NFD_is_NO = isNFD_NO($code_point) — boolean of the derived property NFD_NO (NFD_Quick_Check=No).
  • $NFC_is_NO = isNFC_NO($code_point) — boolean of the derived property NFC_NO (NFC_Quick_Check=No).
  • $NFC_is_MAYBE = isNFC_MAYBE($code_point) — boolean of the derived property NFC_MAYBE (NFC_Quick_Check=Maybe).
  • $NFKD_is_NO = isNFKD_NO($code_point) — boolean of the derived property NFKD_NO (NFKD_Quick_Check=No).
  • $NFKC_is_NO = isNFKC_NO($code_point) — boolean of the derived property NFKC_NO (NFKC_Quick_Check=No).
  • $NFKC_is_MAYBE = isNFKC_MAYBE($code_point) — boolean of the derived property NFKC_MAYBE (NFKC_Quick_Check=Maybe).

That's the whole quick-check crew, bestie — they're literally just vibe checks for code points 🫶.

✨ EXPORT ✨

  • NFC, NFD, NFKC, NFKD — these four are yours by default, no asking required 🎀.
  • normalize and other some functions — those you gotta request. On request only, iykyk.

💀 CAVEATS 💀

Okay bestie, grab a snack, this part is giving "read the fine print" energy. But it matters, so:

Perl's version vs. Unicode version 🌈

This is the big one: since this module refers to perl core's Unicode database in the directory /lib/unicore (or formerly /lib/unicode), the Unicode version of normalization that actually gets implemented by this module depends on what has been compiled into your perl. So like... your perl's age is showing, and it shows in your normalization 😭.

The following table lists the default Unicode version that comes with various perl versions. Also quick heads-up: it is possible to change the Unicode version in any perl version to be any earlier Unicode version, so one could cause Unicode 3.2 to be used in any perl version starting with 5.8.0. Read $Config{privlib}/unicore/README.perl for the deets.

    perl's version     implemented Unicode version
       5.6.1              3.0.1
       5.7.2              3.1.0
       5.7.3              3.1.1 (normalization is same as 3.1.0)
       5.8.0              3.2.0
         5.8.1-5.8.3      4.0.0
         5.8.4-5.8.6      4.0.1 (normalization is same as 4.0.0)
         5.8.7-5.8.8      4.1.0
       5.10.0             5.0.0
        5.8.9, 5.10.1     5.1.0
       5.12.x             5.2.0
       5.14.x             6.0.0
       5.16.x             6.1.0
       5.18.x             6.2.0
       5.20.x             6.3.0
       5.22.x             7.0.0

Correction of decomposition mapping 🙈

So in older Unicode versions, a small number of characters — all of which are CJK compatibility ideographs as far as they have been found — may have an erroneous decomposition mapping (peep lib/unicore/NormalizationCorrections.txt). Anyway, this module will neither refer to lib/unicore/NormalizationCorrections.txt nor provide any specific version of normalization. Which means: this module running on an older perl with an older Unicode database may use the erroneous decomposition mapping blindly, conforming to the Unicode database. Yeah. Blindly. It said what it said 💀.

Revised definition of canonical composition 🦋

In Unicode 4.1.0, the definition D2 of canonical composition (which affects NFC and NFKC, fyi) has been changed — see Public Review Issue #29 and recent UAX #15. This module has used the newer definition since the version 0.07 (Oct 31, 2001). And this module will not support the normalization according to the older definition, even if the Unicode version implemented by perl is lower than 4.1.0. So no retro era for us, we stay in the new-definition timeline, periodt ✨.

👑 AUTHOR 👑

SADAHIRO Tomoyuki <SADAHIRO@cpan.org>

Currently maintained by <perl5-porters@perl.org>

Copyright(C) 2001-2012, SADAHIRO Tomoyuki. Japan. All rights reserved. 🎀

⭐ LICENSE ⭐

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself. Slay, permissive licensing, we love to see it 💖.

🌸 SEE ALSO 🌸

And that's the page, bestie 🫶💜 — this was perl v5.42.3 documentation dated 2026-11-03, aka the Unicode::Normalize(3pm) glow-up. Go normalize something responsibly, mwah 💅✨

📦 where this page comes from